High stiffness polypropylene impact copolymer

Abstract

Disclosed is a polypropylene with an MFR of at least 20 g/10 min comprising a homopolypropylene and optionally within a range from 2 wt % to 30 wt % of an propylene-α-olefin copolymer by weight of the polypropylene; wherein the homopolypropylene has a MFR within a range from 30 g/10 min to 200 g/10 min, an Mw/Mn within a range from 7 to 16, and comprising 1.1 wt % or less atactic polypropylene based on the total weight of the homopolypropylene and atactic polypropylene, where the propylene-α-olefin copolymer has within a range from 30 wt % to 50 wt % α-olefin derived units by weight of the propylene-α-olefin copolymer, and an intrinsic viscosity within a range from 4 to 8 dL/g. The impact copolymer may be obtained by combining a Ziegler-Natta catalyst having at least two different internal electron donors with propylene in reactors in series to produce the homopolypropylene followed by a gas phase reactor to produce a propylene-α-olefin copolymer.

The invention claimed is: 
     
       1. An impact copolymer comprising:
 a homopolypropylene having a melt flow rate of at least 20 g/10 min (ASTM D1238, 230° C., 2.16 kg), an Mw/Mn within a range from 7 to 16, and an Mz/Mw within a range from 7 to 16, and comprising 1.1 wt % or less of atactic polypropylene based on a total weight of the homopolypropylene and the atactic polypropylene; and 
 within a range from 2 wt % to 30 wt % of a propylene-α-olefin copolymer, by weight of the impact copolymer;
 wherein the impact copolymer has a melt flow rate within a range of 60 g/10 min to 160 g/10 min (ASTM D1238, 230° C., 2.16 kg); and 
 wherein the propylene-α-olefin copolymer is prepared by a gas phase polymerization reaction in the presence of the homopolypropylene, such that at least some of the homopolypropylene and the propylene-α-olefin copolymer are linked to one another, and the propylene-α-olefin copolymer is embedded in a continuous matrix of the homopolypropylene wherein the propylene-α-olefin copolymer comprises within a range from 30 wt % to 43 wt % α-olefin derived units by weight of the propylene-α-olefin copolymer. 
 
 
     
     
       2. The impact copolymer of  claim 1 , wherein the propylene-α-olefin copolymer has an intrinsic viscosity within a range from 4 to 8 dL/g. 
     
     
       3. The impact copolymer of  claim 1 , wherein the propylene-α-olefin copolymer comprises α-olefin derived units that are selected from the group consisting of ethylene, C4 to C8 α-olefin derived units, and combinations thereof. 
     
     
       4. The impact copolymer of  claim 1 , wherein a crystalline portion of the propylene-α-olefin copolymer is 3 wt % or less relative to a total amount of propylene-α-olefin copolymer. 
     
     
       5. The impact copolymer of  claim 1 , wherein the impact copolymer has a flexural modulus of at least 1500 MPa. 
     
     
       6. The impact copolymer of  claim 1 , wherein the impact copolymer has an Izod impact strength (23° C.) of at least 4 kJ/m 2 . 
     
     
       7. The impact copolymer of  claim 1 , wherein the impact copolymer is obtained by combining a Ziegler-Natta catalyst with propylene in two slurry polymerization reactors in series to produce the homopolypropylene, followed by combining the homopolypropylene and the Ziegler-Natta catalyst with propylene and an α-olefin in a gas phase reactor. 
     
     
       8. The impact copolymer of  claim 7 , wherein the Ziegler-Natta catalyst has at least two different internal electron donors. 
     
     
       9. The impact copolymer of  claim 7 , wherein the Ziegler-Natta catalyst comprises a dialkyl- and/or dialkoxymagnesium support having an average particle size within a range from 5 μm to 120 μm. 
     
     
       10. An impact copolymer with a MFR within a range from 60 g/10 min to 140 g/10 min (230° C., 2.16 kg) consisting essentially of a homopolypropylene and within a range from 4 wt % to 10 wt % of an ethylene-propylene copolymer (EPR) by weight of the impact copolymer; wherein the homopolypropylene has a MFR within a range from 80 g/10 min to 200 g/10 min (230° C., 2.16 kg), an Mw/Mn within a range from 8 to 15, an Mz/Mw within a range from 7 to 16, and comprising 1.1 wt % or less atactic polypropylene based on the total weight of the homopolypropylene and atactic polypropylene; and the EPR has within a range from 30 wt % to 50 wt % ethylene derived units by weight of the EPR, and an intrinsic viscosity within a range from 4 to 7 dL/g; and the impact copolymer is obtained by combining a Ziegler-Natta catalyst with propylene in two slurry polymerization reactors in series to produce the homopolypropylene, followed by combining the homopolypropylene and Ziegler-Natta catalyst with propylene and ethylene in a gas phase reactor to produce the EPR that is linked to the homopolypropylene, where the Ziegler-Natta catalyst comprises to different internal electron donors wherein the propylene-α-olefin copolymer comprises within a range from 30 wt % to 43 wt % α-olefin derived units by weight of the propylene-α-olefin copolymer. 
     
     
       11. The impact copolymer of  claim 1 , wherein the homopolypropylene comprises at least a first homopolypropylene and a second homopolypropylene that have melt flow rate values differing by at least 50 g/10 min (ASTM D1238, 230° C., 2.16 kg). 
     
     
       12. The impact copolymer of  claim 11 , wherein the first homopolypropylene has a melt flow rate of 5 g/10 min or less (ASTM D1238, 230° C., 2.16 kg) and the second homopolypropylene has a melt flow rate of 100 g/10 min or more (ASTM D1238, 230° C., 2.16 kg). 
     
     
       13. The impact copolymer of  claim 12 , wherein the melt flow rate of the second homopolypropylene is within a range of 100 g/10 min to 1000 g/10 min (ASTM D1238, 230° C., 2.16 kg). 
     
     
       14. The impact copolymer of  claim 1 , wherein the melt flow rate of the homopolypropylene is within a range of 80 g/10 min to 160 g/10 min (ASTM D1238, 230° C., 2.16 kg). 
     
     
       15. The impact copolymer of  claim 1 , wherein the impact copolymer consists essentially of the homopolypropylene and the propylene-α-olefin copolymer. 
     
     
       16. The impact copolymer of  claim 1 , wherein the impact copolymer comprises within a range from 2 wt % to 20 wt % of the propylene-α-olefin copolymer, by weight of the impact copolymer. 
     
     
       17. The impact copolymer of  claim 1 , wherein the impact copolymer consists of the homopolypropylene and the propylene-α-olefin copolymer. 
     
     
       18. The impact copolymer of  claim 17 , wherein the impact copolymer has a flexural modulus of at least 1500 MPa without a nucleating agent.